IFREMER researchers have sought to understand why the catch of these small fish have been divided by ten and why they disappear, exhausted, in adulthood.
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Sardines are one of the most fished fish in the world. Since the 2000s, tonnages are drastically decreasing in the Gulf of the Lion where the Mediterranean Sea is the most productive. Fishermen reported another 10,000 to 14,000 tonnes of sardines a year in the 1990s. After a very rapid tumble, they only account for a thousand per year since 2010. According to landing registers dating back to 1865, The catches have never been so weak.
But these small pelagic fish are no less numerous, but their corpulence decreases sharply. Their size has increased from 15 to 11 centimeters and their weight of 30 to 10 grams since the mid-2000s. And adults – aged at least 2 years in a species that can live up to 7 years – have disappeared.
The French Sea Research Institute (Ifremer) wanted to know why. He presented on Monday, November 8, the main conclusions of his work in the Joint Marbec Research Unit (which brings together several organizations and universities on the conservation and exploitation of marine diversity) and funded in particular through the Fund. European for maritime and fishing, FEAMP. “We thought at first that it was a transitional change,” says Jean-Marc fromentin, researcher in Ifremer, who contributed to this work. But the melt of the stock of sardines – like that of anchovies, another pelagic -, proved lasting. Is it the consequence of an overfishing characterized? Or a phenomenon caused by the appetite of a predator, like the red tuna that is better itself or the dolphin, as some fishermen are considering? Or the damage due to one or more epizootics?
Reduction of plankton
The case was taken very seriously. The Mona Lisa project (research on strong natural mortalities and indicators for the management of sardines and mediterranean anchovies) began in 2014. The first step was to test all these assumptions. And to rule out one by one. Sardines and anchovies are little caught on the French Mediterranean coasts unlike Italy; Tunas are only 1% to 2% of this stock of pelagic and no particular virus has been spotted. The researchers have come to conclude that if the sardines are less big, it is because they eat less and if they fast is that the plankton – smaller, less rich and less provided – has decreased about 15%.
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